The present invention relates to a multi-speed transmission for electrical power tools with a rotatable tool, in particular power drills.
A known multi-speed transmission of this type is disclosed for example in the patent document EP 0 566 926 A1. It is formed as a planetary transmission switchable in two speeds. For this purpose its sun gear is mounted on the gear reducer shaft, and the planetary gear carrier supported through a needle bearing on the gear reducer shaft carries an outer toothing which is in constant engagement with a toothed rim which drives the tooth spindle. An arresting toothing is formed on the hollow gear of the planetary transmission provided with inner teeth. The arresting toothing is associated with an arresting piece mounted on the housing, and a peripheral groove is provided for a speed switching slider. Additionally, the planetary carrier is associated with a gear having an outer toothing and connected with the planetary gear carrier through segments guided between the planetary gears. The outer toothing of the gear is formed so that the inner toothing of the hollow gear is insertable into it. In the first speed, the hollow gear is displaced so that it is fixed by an arresting toothing on the arresting piece. The sun gear connected with the gear reducer shaft is thereby is driven through the planetary gears of the planetary gear carrier with a transmission ratio of 1:3.4 in rotation. Through the toothed rim which engages with the outer toothing of the planetary gear carrier, the tooth spindle is thereby driven with a low rotary speed of 700 revolutions per minute. In the second speed, the hollow gear is displaced in its central position, in which it additionally engages in the outer toothing of the gear, so that it is blocked on the planetary gear carrier. The planetary gear carrier is thereby non rotatably connected directly with the sun gear, and the gear rim of the tool spindle is driven with a transmission ratio of 1:1 with a rotary speed of 2250 revolutions per minute.